Hi, Tom!
As far as suspending additives (are you talking about things like oatmeal or dried herbs or something like that?), it helps to let the soap cool quite a bit before pouring into the mold. If the base is too hot, the additives will sink to the bottom (which I guess would really be the top of the soap bar). It stays throughout the bar easier if it's cooler. You can see if it's cool by looking at it after you stir. If everything falls to the bottom, it's probably too warm to suspend. Also, the smaller your additives, the easier they are to suspend. Ground oatmeal, for instance, suspends more easily than whole oats.
As far as embeds go, like smaller soaps inside a larger bar, I pour maybe a little less than half my mold with clear (if I'm using single-bar molds) or however much clear layer I want, spritz the clear with rubbing alcohol, spritz the embed with alcohol, place it into the soap (making sure it's not too hot or your embed will melt), and spritz one more time. If you don't want your embed to sink as far down, I guess you could do a thin layer of clear, let it set up, spritz that layer, spritz your embed, and then arrange it on the first layer and then finish pouring the rest of your clear (check your temp). Watch out for air bubbles, though.
As far as temperatures go, BB says that the ideal temp is 120-130 degrees, but I pour closer to 120. Even at 120, I still sometimes have trouble with melty, tendril-y layers or embeds.
Hope that helps. Have fun soaping!
